Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$64.73	3.848%	$67.2208	$67.22	$67.20	$67.20
Purchase #2	$113.65	3.287%	$117.3857	$117.39	$117.40	$117.40
Purchase #3	$211.35	5.461%	$222.8918	$222.89	$222.90	$222.90
Purchase #4	$122.64	8.129%	$132.6094	$132.61	$132.60	$132.60
Purchase #5	$201.77	10.712%	$223.3836	$223.38	$223.40	$223.40
Purchase #6	$172.85	3.480%	$178.8652	$178.87	$178.85	$178.90
Purchase #7	$185.79	3.260%	$191.8468	$191.85	$191.85	$191.80
7 purchase totals =	$1,072.78		$1,134.2033	$1,134.21	$1,134.20	$1,134.20